A great advantage of the rotary steam engine is that the steam can be generated by a number of fuels, and preferably by those that create little or no pollution.
Rotary engines of the type to which the present invention relates are described, for example, in U.S. Pat. No. 866,808. They comprise a housing formed with an inner chamber having at least two overlapping, parallel-axis cylindrical portions, each with a shaft passing therethrough. On one shaft there is a cylindrical drive rotor which is provided with a radially outwardly extending piston tooth or projection, and which forms an annular working chamber with the housing wall surrounding it. On the other shaft, which rotates in the opposite direction, there is provided a cylindrical abutment rotor which runs along the housing wall and rides on the working rotor. The abutment rotor has a radially inwardly directed recess or indenture for the passage of the piston tooth or projection therethrough. Steam entering the annular working chamber at a steam inlet port moves the projection to rotate the drive rotor, and exits through an exhaust port formed in the wall of the chamber. The abutment rotor recess receives the drive rotor projection as the projection approaches the abutment rotor and permits it to pass the same. Rolling engagement between the cylindrical surfaces of the drive and abutment rotors prevents the steam from completing a circle of revolution within the annular working chamber. Sealing between the rotors and the casing is achieved by side plates that bolt to the casing to close the chamber cylindrical portion ends. Frictional contact between the moving rotor parts and the side plates subjects the drive rotor to considerable wear and is a major source of steam leakage.
Other prior art arrangements of interest are disclosed in U.S. Pat. Nos. 3,620,655; 4,202,315; and 4,464,102.